Not surprisingly, you are getting varied responses, so you’ll have to go with your gut. Where do you most see yourself? There is no wrong choice here, obviously.
If it were me: 1) Yale, 2) Stanford, 3) Harvard. Why? As @prezbucky notes, Yale is the most undergraduate-focused of the three. Your post shows a strong preference for a school where you will not feel ignored, left out, or be seen as a number, a cog in the larger machine. Plus, as you also note, Yale has its very attractive residential houses. On the other hand, if the undergrad experience that you seek is more of a social thing, perhaps Harvard and Stanford are stronger in this regard.
When many of us say that there is no wrong choice, this is not just a tired line (or it is perhaps a tired line, but it’s true). Where do you most see yourself? Which school, if it were suddenly to be ripped away from you as an option, would you feel most bummed about? You know that you’ll be somewhere in the fall, so which school immediately comes to mind (before the other two step in and you start picturing yourself there)?
College decisions are odd in that they are both very significant but not that significant at the same time (I am talking about when choosing among two or three peer institutions).
So, you have visited all three, and found neither slam-dunks nor deal-killers in terms of the “vibe,” campus aesthetic, weather, surrounding area, etc.
It seems, then, that you would likely have a terrific social and classroom experience at any of the three. You can compare blemishes and juggle pros and cons, but let’s face it, if you’d only gotten into one, you’d be having no qualms about committing. Each would be great in its own way. You’re not saying that there’s any significant financial or logistical difference that would sway you.
I would say, then, that your passion for Latinx and immigration issues should draw you to California. Go to Stanford, where you will have a wealth of research and activism opportunities at your fingertips. Assuming you’re probably bilingual, your language skills and cultural competency will open even more doors for involvement in research and advocacy. The Latinx community is far more dilute in the Northeast. California is a better social laboratory for your interests. Don’t worry about the prominence of STEM; social sciences and humanities are equally stellar and well-funded. In terms of liberal sensibility, the juxtaposition of social consciousness with elitism will create a measure of cognitive dissonance at all of these schools, but Stanford’s less old-money vibe will probably grate the least. To me it seems the obvious choice for you. But that’s only because there’s no other factor clearly swinging your choice in another direction. There’s no wrong choice here, as you well know.
Congratulations!